Well, just because I'm not offering an opinion on GREs anymore, it doesn't mean we can't have a helpful thread on here to help people out.
If you've got insight into good preparation books and materials, or websites for that matter. Add them to the comments section. Here's what we have from two readers on the previous post:
Does anyone have a good book to recommend for reviewing math concepts and skills for the GRE? Maybe something geared toward the English major who hasn't done math in six years?
The Princeton Review book has good explanations for the math concepts. I bought the Barron's book and found it helpful (it has a ton of exercises and practice tests), but its explanations made me feel like a math dunce (it's been 12 years without math for me). Then a friend gave me The Princeton Review book, and I realized it wasn't me, it was the book... Of course, we'll see how well I do when I actually take the test next month.